Fatigue Resistance of Dental Implants With Different Fixture-Abutment Connections

Objectives: The aim of this study was to evaluate fatigue resistance of dental implants with two different fixture-abutment connections by in vitro fatigue testing and in silico three-dimensional finite element analysis (3D FEA) using original computer-aided design (CAD) models.
Methods: Dental implant fixtures with external connection (EX) or internal connection (IN) abutments were fabricated from original CAD models using grade IV titanium, and step-stress accelerated life-testing was performed. Fatigue cycles and loads were assessed by Weibull analysis, and fatigue cracking was observed by micro-computed tomography and a stereomicroscope with high dynamic range software. Using the same CAD models, displacement vectors of implant components were analysed by 3D FEA. Angles of the fractured line occurring at fixture platforms in vitro and of displacement vectors corresponding to the fractured line in silico were compared by two-way ANOVA.
Results: Greater reliability at 1000 N, 1200 N, and 1400 N were recorded for IN (94.0%, 77.6%, and 43.2%) than EX (86.3%, 40.7%, and 1.6%). Fatigue crack initiation was primarily observed at implant fixture platforms. FEA demonstrated that displacement vectors of the implant fixtures were distributed in the same direction at crack lines observed in vitro for both implant systems (p=0.324).
Conclusions: In silico displacement vectors in the implant fixture are insightful for geometric development of dental implants to reduce complex interactions leading to fatigue failure.